EP2097741B1 - Simplified impedance plane bond testing inspection by ultrasonic means - Google Patents
Simplified impedance plane bond testing inspection by ultrasonic means Download PDFInfo
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- EP2097741B1 EP2097741B1 EP07867383.7A EP07867383A EP2097741B1 EP 2097741 B1 EP2097741 B1 EP 2097741B1 EP 07867383 A EP07867383 A EP 07867383A EP 2097741 B1 EP2097741 B1 EP 2097741B1
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Definitions
- Embodiments of the present disclosure relate generally to ultrasonic inspections of structures. More particularly, embodiments of the disclosure relate to systems and methods for non-destructive ultrasonic inspections of sub-surface portions of layered structures.
- Laminate composite materials are becoming increasingly common in the constructions of large aircraft. Typical laminate composite materials are composed of layered resin bonded graphite textiles. Like any material disposed along the exterior of an aircraft, laminate composite materials are subject to damages during the service life of an aircraft. In-flight collisions with birds and air-borne debris, and ground collisions involving loading and maintenance vehicles and equipment cause visible impact sites along the exterior of an aircraft. Assessments and repairs of laminate composite materials represent significant challenges with regard to efficiencies in time, cost, and training. Ground maintenance crews may be able to recognize impact sites along aircraft exteriors, but are typically not sufficiently trained or equipped to assess internal damages that may be associated with visible impact sites.
- NDI Non-destructive inspection
- a bond-testing apparatus according to an example of prior art is disclosed in the U.S. Patent No. 4,215,583 issued to Botsco et al. on August 5, 1980 .
- This patent describes a sonic energy probe that receives a sinusoidal reference signal from an oscillator and develops an output signal that contains phase and amplitude data.
- the phase and amplitude data contained by the output signal developed by the probe are affected by properties of an inspected structure coupled to the probe.
- the phase difference between the reference signal and the output signal tends to increase with the depth of the disbond.
- the amplitude of the output signal tends to decrease with the depth of the disbond.
- a complex impedance plane display when the amplitude and phase difference are related respectively to radius and angle in a two-dimensional polar coordinate display called a complex impedance plane display, typical data points fall along a spiral pattern. Shallow disbonds are represented in outer portions of the spiral pattern, and deeper disbonds are represented in inner portions of the spiral pattern, for example, as shown in FIG. 3 of the above-identified patent to Botsco et al. While the position of a data point in a complex impedance plane display may provide information about the condition of a structure under inspection, a high degree of training is needed for understanding and using the described apparatus. Thus, like other available NDI approaches, the technology described in the patent to Botsco et al. appears to be in the practice domain of highly trained specialists. This has been proven to be the case in the commercial embodiments of the technology described in the patent to Botsco et al.
- Trained NDI specialists and the complex equipment they may need to deploy are not typically immediately available at commercial aviation facilities. If specialists are to be summoned every time an impact site along the exterior of an aircraft is noticed, flight delays will occur, and passengers may need to be re-routed and possibly accommodated with hotel rooms and meals.
- Embodiments of the disclosure may address at least some of the above needs and achieve other advantages.
- the disclosure relates to a method of inspecting a structure according to claim 1.
- the inspection system includes an analog signal-processing portion 102 and a digital processing portion 104.
- an oscillator 110 produces a sinusoidal reference signal 111 that is applied to a combination of a resistor 112 and an ultrasonic transducer 114.
- the reference signal is generally preset to a frequency associated with the natural resonating frequency for a given ultrasonic transducer.
- the ultrasonic transducer 114 is placed in contact and coupled through a liquid medium with a layered structure under inspection, the complex impedance of the transducer 114 is affected by the physical characteristics of the structure.
- the response signal 115 developed by the transducer 114 has phase and amplitude characteristics that are generally representative of the structure under inspection, and that are more particularly representative of the locations of defects such as bond flaws between the various layers of the structure.
- the response signal 115 is applied to a buffer amplifier 116, which produces the signal 117 that has phase and amplitude characteristics derived from those of response signal 115.
- the sinusoidal signal 111 is further applied to an inverting amplifier 118, which, in conjunction with a potentiometer 120, produces a signal 121.
- the reference signal 111 is also applied to an integrating amplifier 122, which, in conjunction with an inverting amplifier 124 and potentiometer 126, produces a signal 127.
- Signal 121 and signal 127 represent quadrature-phase separated components of the response signal 115 developed by the transducer 114.
- the signals 121,127, and 117 are applied to a summing junction 132 to produce a signal 133, which represents the complex impedance of the transducer 114 as affected by any flaws present in the bonding between layers of a laminate structure under inspection.
- the signal 133 is applied to a buffer amplifier 134, the output signal 135 of which is applied to one terminal of a potentiometer 136.
- reference signals 143 and 145 are provided respectively by voltage comparators 142 and 144.
- the 152 and 154 circuits respectively provide the first and second component signals 153 and 155.
- the first component signal 153 may be mathematically described as Ep(cos(phi)), and the second component signal 155 as Ep(sin(phi)), where phi represents the phase characteristic of the signal 133.
- the first and second component signals 153 and 155 have amplitudes that are proportional to quadrature-phase separated components of the signal 133 which, when the transducer 114 is placed in contact or coupling with a structure under inspection, represents the condition of the structure.
- Analog signal-processing in complex impedance plane analysis circuits is described in further detail in the U.S. Patent No. 4,215,583, which issued to Botsco et al. on August 5, 2003 .
- quadrature-phase separated components of a sinusoidal signal are used as coordinates in two-dimensional displays that represent vector tips in a complex impedance plane and that convey information relating to the amplitudes and phases of signals influenced by bond flaws within an inspected structure.
- the first and second component signals 153 and 155 can be related to impedance plane coordinates.
- the impedance plane coordinates described herein are determined by sampling the first and second component signals 153 and 155 respectively at the 152 and 154 circuits.
- the digital processing portion 104 of the system 100 receives the first and second component signals 153 and 155, and, as described in the following, an indicator 106 alerts an operator to the presence of a bond flaw when the transducer 114 is disposed into contact or coupling with a damaged or delaminated layered structure without regard to whether a typical operator views a two-dimensional display.
- the digital processing portion 104 comprises an analog-to-digital converter (ADC) 160, which receives the first and second component signals 153 and 155 and generates respectively corresponding digital data signals 163 and 165.
- ADC analog-to-digital converter
- the digital data signals 163 and 165 are communicated to a programmable logic chip (PLC) 162.
- PLC programmable logic chip
- the PLC 162 is programmed to analyze the corresponding digital data signals while calculating the impedance plane relationships between the signals and activating an indicator 106, which can be, for example, a light-emitting diode (LED) or other light source, when evidence of the presence of a disbond or other flaw is detected.
- an indicator 106 which can be, for example, a light-emitting diode (LED) or other light source, when evidence of the presence of a disbond or other flaw is detected.
- LED light-emitting diode
- FIG. 2 an example of a reference signal 111 produced by the oscillator 110 ( FIG. 1 ) is shown.
- the first axis 202 represents time and the vertical axis 204 represents time-varying voltage values. While FIG. 2 relates generally to other time and voltage domains, in this example the reference signal 111 has a maximum amplitude of several volts and a frequency of approximately 239 kilo-Hertz.
- the reference signal 111 is shown with several curves representing the response signals 115 developed by the transducer 114 under several different load conditions. It should be understood that FIGS. 2-5 depict simulated signals and coordinates determined therefrom.
- a first response signal 115A corresponds to a calibration condition and is exhibited when the activated transducer 114 ( FIG. 1 ) is disposed into contact or coupling with a good structure that is free of disbonds and flaws in the vicinity of the transducer.
- a second response signal 115B corresponds to a lift-off condition and is exhibited, upon activation by the oscillator 110, when the transducer 114 is out of coupling with a surface to be inspected.
- a third response signal 115C corresponds to an inspection condition and is exhibited when the activated transducer 114 is disposed into contact or coupling with a structure under inspection.
- the third response signal 115C has phase and amplitude characteristics that differ from those of the first response signal 115A.
- the third response signal 115C provides evidence that the structure under inspection may have a disbond or other defect in the vicinity of the transducer.
- the signals depicted in FIG. 2 are represented as coordinates disposed within a two-dimensional complex impedance plane 300 defined by a first axis 302 and a second axis 304, which is perpendicular to the first axis 302.
- the impedance plane coordinates 315A, 315B, and 315C in FIG. 3 correspond respectively to the first, second, and third response signals 115A, 115B, and 115C in FIG. 2 .
- Each of the impedance plane coordinates 315A, 315B, and 315C in FIG. 3 are defined by a first axis coordinate and a second axis coordinate, values of which are determined as shown in FIG. 2 .
- each first axis coordinate in FIG. 3 represents a measured voltage value for the respectively corresponding response signal at the time 208 in FIG. 2 . That is, for example, the first axis coordinate 302B of the impedance plane coordinates 315B in FIG. 3 represents the value of the response signal 115B in FIG. 2 at the time 208.
- the time 208 ( FIG. 2 ) is spaced from the time 206 along the time axis 202 by one quarter of the oscillatory period of the sinusoidal reference signal 111.
- the time 208 can be described as disposed ninety degrees from the zero-voltage crossing, at time 206, of the reference signal 111.
- the first axis and second axis coordinates in FIG. 3 can be described as quadrature-phase separated components of the response signals to which the impedance plane coordinates respectively correspond. It should be understood that, while they are graphically illustrated together in FIG.
- the response signals 115A, 115B, and 115C are not generated simultaneously as they represent varying physical dispositions of the transducer 114 ( FIG. 1 ). It should be further understood that the times 206 and 208 are defined in relation to the periodic zero-voltage crossing times of the sinusoidal reference signal 111, such that the times 206 and 208 are repeated with each sinusoidal cycle of the reference signal.
- the impedance plane coordinates 315A in FIG. 3 correspond to the first response signal 115A ( FIG. 2 ) of the calibration condition with the activated transducer disposed into contact or coupling with a good structure
- the coordinates 315A are identified herein as examples of impedance-plane calibration coordinates 315A.
- the coordinates 315B in FIG. 3 are identified herein as impedance plane lift-off coordinates 315B
- the coordinates 315C are identified as impedance plane inspection coordinates 315C.
- the PLC 162 in FIG. 1 receives the digital data signals 163 and 165, and is prompted to record these signals when a user actuates first and second switches 170 and 172.
- first switch 170 the user intends the condition of the transducer 114 to serve as the calibration condition.
- the PLC 162 records the digital data signals 163 and 165 as impedance plane calibration coordinates along the first axis 302 and second axis 304, respectively, in FIG. 3 .
- the second switch 172 the user intends the condition of the transducer to serve as the lift-off condition.
- the PLC 162 records the digital data signals 163 and 165 as impedance plane lift-off coordinates along the first axis 302 and second axis 304, respectively.
- the PLC 162 ( FIG. 1 ) defines a lift-off translation function that may be applied to the incoming digital data signals 163 and 165 to translate from impedance plane inspection coordinates into a lift-off coordinate system.
- the disposition of the inspection coordinates may vary in time as the user moves the transducer 114 into various positions along a structure under inspection and may encounter varying structure conditions such as defects.
- the impedance plane inspection coordinates 315C in FIG. 3 may vary in real-time.
- the inspection coordinates 315C in this example do not coincide with the calibration coordinates 315A.
- the inspection coordinates 315C provide evidence that the structure under inspection may have a disbond or other defect in the vicinity of the transducer.
- the determined impedance-plane inspection coordinates will typically fall along a spiral path.
- a simulated spiral path 306 is shown in FIG. 3 .
- the spiral path 306 spirals inward from the lift-off coordinates 315B, which correspond to zero depth, to the calibration coordinates 315A, which correspond to the depth of a good undamaged structure.
- Typical inspection coordinates corresponding to disbonded or damaged portions of an inspected structure will typically fall somewhere along the spiral path 306 such that the position of the inspection coordinates along the path reveals the depth of a detected disbonded or damaged layer of the structure.
- Relatively shallow disbonds will typically be represented by inspection coordinates along the spiral path 306 toward the lift-off coordinates 315B.
- Relatively deep disbonds will typically be represented by inspection coordinates toward the calibration coordinates 315A.
- the inspection coordinates 315C fall along an outer portion of the spiral path 306, and toward the lift-off coordinates 315B. This provides evidence that the structure under inspection may have a shallow disbond or other defect in the vicinity of the transducer.
- the PLC 162 ( FIG. 1 ) generally rotates the impedance plane coordinates represented in FIG. 3 using the lift-off translation function. Such rotations produce rotated impedance plane coordinates as shown in FIG. 4 and 5 , which represent examples of embodiments of the present disclosure with regard to conditions under which the PLC 162 activates the indicator 106 ( FIG. 1 ).
- the PLC 162 automatically rotates the impedance plane coordinates 315A, 315B, and 315C until the resulting rotated calibration coordinates 415A and lift-off coordinates 415B reach the first axis 302.
- such a rotation produces rotated inspection coordinates 415C and the rotated spiral path 406. Points along the rotated spiral path 406 in FIG. 4 relate in one-to-one correspondence with points along the spiral path 306 in FIG. 3 .
- the lift-off translation function effectively rotates the impedance plane coordinates, which rotating may be described as equivalent to shifting the times at which the voltage values of response signals are measured in determining the coordinates. That is, each of the rotated impedance plane coordinates in FIG. 4 has a second axis coordinate representing a voltage value measured at the time 210 in FIG. 2 , and a first axis coordinate representing a measurement at the time 212.
- the respective correspondence of the calibration coordinates 415A ( FIG. 4 ), lift-off coordinates 415B, and inspection coordinates 415C with the response signals 115A ( FIG. 2 ), 115B, and 115C is maintained throughout the rotation.
- the shifted times 210 and 212 at which the response signals are measured in determining the rotated coordinates lag the times 206 and 208 respectively by a common time shift that is equivalent to the angular rotation represented by FIG. 4 .
- the times 210 and 212 in FIG. 2 are separated by one quarter of the oscillatory period of the sinusoidal reference signal 111. Therefore, the rotated first axis and second axis coordinates in FIG. 4 can be described as quadrature-phase separated components of the response signals to which the rotated impedance plane coordinates respectively correspond.
- the PLC 162 ( FIG. 1 ) activates the indicator 106 if the rotated inspection coordinates 415C are at least disposed above the first axis 302. This generally indicates an alarm condition wherein the rotated inspection coordinates, such as inspection coordinates 415C, are not coincident with the rotated calibration coordinates 415A.
- the PLC 162 ( FIG. 1 ) may be configured to activate the indicator 106 if the rotated inspection coordinates 415C are at least disposed above the first axis 302, and spaced from the first axis by at least a preset threshold 408. As shown in FIG.
- the inspection system 100 comprises an adjustment device 174, such as a turn-potentiometer, for adjustment of the preset threshold 408, which may be adjusted to avoid spurious alarm indications when, for example, rotated inspection coordinates fall negligibly above the rotated calibration coordinates 415A.
- an adjustment device 174 such as a turn-potentiometer
- the PLC 162 ( FIG. 1 ) automatically rotates the impedance plane coordinates 315A, 315B, and 315C ( FIG. 3 ) until the resulting rotated lift-off coordinates 515B ( FIG. 5 ) are disposed above the first axis 302 and spaced from the first axis by at least the preset threshold 408. As shown in FIG. 5 , such a rotation produces rotated calibration coordinates 515A, rotated inspection coordinates 515C, and the rotated spiral path 506. In the example of FIG. 5 , the PLC 162 ( FIG. 1 ) automatically rotates the impedance plane coordinates 315A, 315B, and 315C ( FIG. 3 ) until the resulting rotated lift-off coordinates 515B ( FIG. 5 ) are disposed above the first axis 302 and spaced from the first axis by at least the preset threshold 408. As shown in FIG. 5 , such a rotation produces rotated calibration coordinates 515A, rotated inspection coordinates 515C
- the indicator 106 ( FIG. 1 ) activates the indicator 106 if the rotated inspection coordinates 515C are at least disposed above the first axis 302 and spaced from the first axis by at least the preset threshold 408.
- the indicator 106 ( FIG. 1 ) is activated to alert an operator if liquid coupling between the transducer 114 and an inspected structure is lost. Such a loss of coupling may cause the generation of rotated impedance plane coordinates near or at coincidence with the rotated lift-off coordinates 515B.
- an operator is alerted when inadvertent lift-off and coupling-loss conditions occur, prompting the operator to restore couplant or re-scan the area.
- the disposition of rotated inspection coordinates above the preset threshold 408 causes activation of the indicator 106 ( FIG. 1 ).
- This establishes one or more depth ranges within which the inspection system 100 indicates disbonds within an inspected structure.
- a first depth range is established along a first portion 510 of the rotated spiral path 506 between the rotated lift-off coordinates 515B and a first point 512 defined where the rotated spiral path 506 reaches the preset threshold 408.
- a second depth range is established above the threshold 408 and along a second portion 514 of the rotated spiral path 506 between second and third points 516 and 518, at which points the rotated spiral path 506 reaches the preset threshold 408.
- the first portion 510 represents an outer portion of the rotated spiral path 506
- the second portion 514 represents an inner portion of the rotated spiral path 506.
- the first portion 510 represents a shallow depth range for detected disbonds
- the second portion 514 represents a deeper depth range.
- rotated inspection coordinates falling along either the first portion 510 or the second portion 514 of the rotated spiral path 506 cause activation of the indicator 106 ( FIG. 1 ) to alert an operator to the likely presence of a disbond in an inspected structure.
- Activation of the indicator in the first portion 510 is a condition universal to all structures, independent of the operator choice of structure for initial calibration coordinates 315A.
- FIG. 1 An embodiment of the inspection system 100 ( FIG. 1 ) is shown in various simulated inspection scenarios in FIGS. 6-8 .
- many components of the inspection system 100 are disposed within and protected by a portable housing 600.
- a probe device 602 that includes the ultrasonic transducer 114 ( FIG. 1 ) is connected to the remainder of the system 100 by a cable 604 so that the probe device can be moved about and coupled to structures while the housing 600 is held within view of an operator.
- the first and second switches 170 and 172 are readily available for actuation by an operator intending to establish calibration and lift-off coordinates.
- the adjustment device 174 which establishes the preset threshold 408 ( FIG.
- the indicator 106 is visible along the exterior of the housing so that an operator is made readily aware when an alert condition occurs.
- the inspection device Prior to determining whether damages are present in a structure, the inspection device is calibrated by disposing the probe device 602 ( FIG. 6 ) against a good structure that is free of disbonds and flaws in the vicinity of the probe device, and the first switch 170 is actuated. This establishes calibration coordinates, such as the calibration coordinates 315A in FIG. 3 .
- the operator may choose a portion of a structure under inspection, under the assumption that the portion is free of flaws.
- the assurance of the calibration of the inspection system 100 following such a calibration procedure may be as questionable as any assumption that a good portion of a structure was interrogated.
- a calibration structure can be provided in order to assure that calibration is completed on a well characterized material sample.
- the operator furthermore lifts the probe device 602 from contact with any structure and actuates the second switch 172 to establish lift-off coordinates, such as the lift-off coordinates 315B in FIG. 3 .
- the embodiment of the inspection system 100 shown in FIGS. 6-8 is configured as described herein with regard to FIG. 5 .
- the indicator 106 will be activated to alert an operator if rotated inspection coordinates, for example coordinates 515C ( FIG. 5 ), are disposed above the first axis 302 and spaced from the first axis by at least the preset threshold 408.
- FIG. 6 depicts an exemplary laminate structure 640 capable of being used on any number of structures, such as those found on airplanes, automobiles and other vehicles, or any other structure that can benefit from a light, yet strong material.
- the laminate structure 640 has a front-surface 642 and a back-surface 644, and is composed of multiple individual laminate sheets 646.
- the laminate sheets are joined together by a bonding material.
- the exemplary laminate sheets 646 are composed of sheets of graphite fibers joined by a bonding material composed of an ester based resin.
- these descriptions relate to sheets constructed of other materials. Such other materials include, but are not limited to: carbon-based fabrics; metal foils; bonded metal skins; and polymer-based fabrics such as Kevlar®.
- the laminate structure 640 of FIG. 6 is formed using an ester-based resin, these descriptions relate as well to other bonding materials.
- laminate materials are subject to accidental damages.
- impact damages from birds and airborne debris can occur with every flight.
- the resultant damage will be very light, while in other instances the damage may be moderate to severe.
- the laminate structure 640 in FIG. 6 is depicted as being so lightly damaged that a marking visibly apparent at an impact site 650 is merely superficial and represents no threat to the integrity of the structure.
- the indicator 106 is not activated to alert the operator that any damages are detected below the probe device 602.
- the rotated inspection coordinates in this scenario are coincident with the rotated calibration coordinates 515A ( FIG. 5 ), are disposed below the threshold 408, and are indicative of a structure free of damages.
- the inspection system 100 inspects a laminate structure 740 wherein flaws such as delaminations reside.
- the impact site 750 is disposed above a damaged region of the structure.
- the damage likely began at the impact site along the front surface 742 of the structure and propagated toward the back surface 744 in an expanding cone pattern of disbonds 752 as illustrated.
- Such cone patterns are typical in damaged laminate structures as damages can extend both deeply into a structure and laterally around an impact site.
- the probe device 602 is pressed against structures near the impact sites 650 and 750, respectively.
- the operator can determine that hidden damages are not likely present.
- the rotated inspection coordinates 515C ( FIG. 5 ) are disposed above the first axis 302 and spaced from the first axis by at least the preset threshold 408.
- the indicator 106 is activated to alert the operator that sub-surface damages are detected.
- the inspection system 100 inspects the bondline integrity of a composite repair patch 800 applied to the damaged structure 740 of FIG. 7 .
- Bondline integrity relates to the quality of the bond between a patch and the surface of a structure. If the bond has porosity or voids, the patch may become detached when the structure is returned to service. For example, a repair patch applied to the wing tip or other exterior component of a jet aircraft can be exposed to extreme conditions and can become detached and lost if the bondline integrity of the patch is not sound.
- Typical composite repair patches in the airline industry are either four or eight plies thick.
- the inspection system 100 has been initialized for inspecting the bondline integrity of a four-ply patch 800.
- impedance plane calibration coordinates collected using a calibration shim exceeding the thickness of the four-ply patch, and lift-off coordinates have been established.
- the indicator 106 is not activated in FIG. 8 . This condition provides assurance to the operator that the repair patch 800 is properly applied to the damaged structure at least in the vicinity of the current position of the probe device 602. In performing a thorough inspection, the operator may move the probe device along the perimeter of the patch to determine whether the patch is well attached to the structure 740.
- FIG. 9 is a flow chart representing a method, according to at least one embodiment of the disclosure, of inspecting a structure.
- the inspected structure may be, for example, an aircraft component constructed of multiple layers of composite material.
- the method 900 represented in FIG. 9 initiates at step 910, at which step an ultrasonic transducer is coupled with a first structure portion.
- the first structure portion is assumed or confirmed to be free of defects, and may be, for example, a calibration sample of material intended for use in calibrating the inspection system 100 ( FIG. 7 ).
- a sinusoidal first signal is generated by the ultrasonic transducer and impedance plane calibration coordinates are determined, the calibration coordinates corresponding to quadrature-phase separated components of the first signal.
- the first response signal 115A in FIG. 2 may be generated as the sinusoidal first signal, and the impedance-plane calibration coordinates 315A in FIG. 3 may be determined.
- step 930 the ultrasonic transducer is lifted from the first structure portion.
- step 940 a sinusoidal second signal is generated by the ultrasonic transducer and impedance plane lift-off coordinates are determined, the lift-off coordinates corresponding to quadrature-phase separated components of the second signal.
- the second response signal 115B in FIG. 2 may be generated as the sinusoidal second signal, and the impedance-plane lift-off coordinates 315B in FIG. 3 may be determined.
- the inspection of a structure commences in step 950 ( FIG. 9 ).
- the ultrasonic transducer is coupled with a structure portion to be inspected.
- a structure portion to be inspected For example, an aircraft may be subject to a pre-flight visual inspection and the impact site 750 ( FIG. 7 ), which represents a surface marking, dent, or scratch may come to the attention of a pre-flight inspector. The inspector may not be able to visibly determine whether serious damage is present, and a decision should be made as to whether the aircraft is fit for flying service. Accordingly, in this example, the inspector couples the probe device 602, which includes the ultrasonic transducer 114 ( FIG. 1 ), with the structure 740 under inspection near the impact site as shown in FIG. 7 .
- a sinusoidal third signal is generated by the ultrasonic transducer and impedance plane inspection coordinates are determined, the inspection coordinates corresponding to quadrature-phase separated components of the third signal.
- the third response signal 115C in FIG. 2 may be generated as the sinusoidal third signal, and the impedance-plane inspection coordinates 315C in FIG. 3 may be determined.
- FIG. 9 Rotations of the calibration coordinates, lift-off coordinates, and inspection coordinates are represented in FIG. 9 to occur in step 970. It should be understood this represents that the coordinates are rotated without regard to whether this is accomplished simultaneously.
- the calibration and lift-off coordinates may be rotated prior to the determination of the inspection coordinates in step 960.
- the calibration coordinates, lift-off coordinates, and inspection coordinates are rotated in the method 900 at least until the calibration coordinates and lift-off coordinates reach a first axis.
- FIG. 4 One example of such a rotation is represented in FIG. 4 , wherein the calibration, lift-off, and inspection coordinates are rotated until the calibration coordinates 415A and lift-off coordinates 415B reach the first axis 302.
- FIG. 5 Another example of such a rotation is represented in FIG. 5 , wherein the calibration, lift-off, and inspection coordinates are rotated until the lift-off coordinates 415B are disposed above the first axis 302 and spaced from the first axis by at least the preset threshold 408.
- an indicator is activated if the rotated inspection coordinates are at least disposed above the first axis. Activation of the indicator represents a situation wherein an operator is alerted to the likely presence of a defect in the structure under inspection, for example, as shown in FIG. 7 . If the indicator is activated, the operator may perform further inspections and, if the structure under inspection is an aircraft component, the flight of the aircraft may be delayed or even cancelled. For example, the operator may summon NDI specialists who may utilize additional inspection devices and methods to determine the extent of the damages.
- a branch 990 is shown in FIG. 9 to illustrate optional additional iterations of steps 950 through 980. That is, in at least one embodiment of the method 900, the ultrasonic transducer is disposed sequentially in multiple locations near the impact site. For example, the transducer might be moved among multiple locations that together surround the impact site. At any such location, the operator observes the indicator and determines whether further inspections are performed according to the judgment or training of the operator.
- the additional optional iterations represented by branch 990 may be particularly advantageous in inspecting an aircraft component constructed of multiple layers of composite materials. Damages initiating at the surfaces of such constructions typically propagate in expanding cone-patterns into the structures. Thus, damages may be detected by conducting inspections at multiple surface portions surrounding an impact site.
- a particular advantage of the inspection system 100 ( FIG. 6 ) resides in the simplicity of its indicator 106. This, in a sense, provides go and no-go test results. An operator without sophisticated training in NDI techniques need not be confounded by complex impedance plane graphical displays. Such an operator can be informed, however, of whether or not significant damages likely reside in an inspected structure. If the indicator 106 is not activated during an inspection session, an inspected structure can be dispatched for use. On the other hand, if the indicator 106 is activated as shown in FIG. 7 , the operator can summon specialists trained in inspections, repairs, and repair assessments.
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Description
- Embodiments of the present disclosure relate generally to ultrasonic inspections of structures. More particularly, embodiments of the disclosure relate to systems and methods for non-destructive ultrasonic inspections of sub-surface portions of layered structures.
- Laminate composite materials are becoming increasingly common in the constructions of large aircraft. Typical laminate composite materials are composed of layered resin bonded graphite textiles. Like any material disposed along the exterior of an aircraft, laminate composite materials are subject to damages during the service life of an aircraft. In-flight collisions with birds and air-borne debris, and ground collisions involving loading and maintenance vehicles and equipment cause visible impact sites along the exterior of an aircraft. Assessments and repairs of laminate composite materials represent significant challenges with regard to efficiencies in time, cost, and training. Ground maintenance crews may be able to recognize impact sites along aircraft exteriors, but are typically not sufficiently trained or equipped to assess internal damages that may be associated with visible impact sites.
- Damages within a composite aircraft component tend to initiate at impact sites and propagate into structures in expanding cone patterns. Unfortunately, visible impact sites that represent mere superficial markings are not easily distinguished by visual inspection from those overlying significant internal damages. Non-destructive inspection (NDI) devices are available so that inspections can reveal hidden sub-surface damages. However, typical available technologies require considerable training and experience.
- For example, a bond-testing apparatus according to an example of prior art is disclosed in the
U.S. Patent No. 4,215,583 issued to Botsco et al. on August 5, 1980 . This patent describes a sonic energy probe that receives a sinusoidal reference signal from an oscillator and develops an output signal that contains phase and amplitude data. The phase and amplitude data contained by the output signal developed by the probe are affected by properties of an inspected structure coupled to the probe. When the probe is disposed against a layered structure having a disbond, the phase difference between the reference signal and the output signal tends to increase with the depth of the disbond. The amplitude of the output signal tends to decrease with the depth of the disbond. Thus, when the amplitude and phase difference are related respectively to radius and angle in a two-dimensional polar coordinate display called a complex impedance plane display, typical data points fall along a spiral pattern. Shallow disbonds are represented in outer portions of the spiral pattern, and deeper disbonds are represented in inner portions of the spiral pattern, for example, as shown inFIG. 3 of the above-identified patent to Botsco et al. While the position of a data point in a complex impedance plane display may provide information about the condition of a structure under inspection, a high degree of training is needed for understanding and using the described apparatus. Thus, like other available NDI approaches, the technology described in the patent to Botsco et al. appears to be in the practice domain of highly trained specialists. This has been proven to be the case in the commercial embodiments of the technology described in the patent to Botsco et al. - Despite the complexities of aircraft inspection technologies, many of the challenges faced in commercial aviation can be understood at a level where basic human safety, customer satisfaction, and economic feasibilities are the critical issues. A typical scenario faced by commercial airlines occurs when a ground maintenance crew member spots an impact site along the exterior of an aircraft as the craft is serviced between flights. A decision must be made as to whether the aircraft should be permitted to fly or should be grounded for thorough inspections, damage assessments, and repairs if necessary. Consequences can be severe when such a decision is poorly made. Both safety and commercial viability must be preserved. Thus an aircraft with significant subsurface damages along a wing or other structure should be grounded, and an aircraft having mere surface markings but no structural damages should be dispatched for flight. Trained NDI specialists and the complex equipment they may need to deploy are not typically immediately available at commercial aviation facilities. If specialists are to be summoned every time an impact site along the exterior of an aircraft is noticed, flight delays will occur, and passengers may need to be re-routed and possibly accommodated with hotel rooms and meals.
- Thus, it would be advantageous to provide devices and methods for inspecting structures by modes requiring minimal training and interpretive expertise. Simplified methods in inspecting layered structures are needed. A need exists for rapid results providing go and no-go indications in NDI inspections.
- Embodiments of the disclosure may address at least some of the above needs and achieve other advantages. The disclosure relates to a method of inspecting a structure according to
claim 1. - Having thus described the disclosure in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and which are briefly described below.
-
FIG. 1 illustrates an ultrasonic inspection system, in accordance with at least one embodiment of the present disclosure, having an ultrasonic transducer, an analog signal processing circuit portion, a digital processing circuit portion, and an indicator for alerting an operator when damages are detected. -
FIG. 2 is a graphical representation of response signals, developed under several different load conditions, by the transducer of the system ofFIG. 1 . -
FIG. 3 is a graphical representation of an impedance plane wherein the response signals ofFIG. 2 are represented as coordinates. -
FIG. 4 is a graphical representation of an impedance plane wherein the impedance plane coordinates ofFIG. 3 are rotated and an alert threshold is defined. -
FIG. 5 is a graphical representation of an impedance plane wherein the impedance plane coordinates ofFIG. 3 are rotated such that a lift-off condition during an inspection session corresponds to coordinates that are disposed above the threshold defined inFIG. 4 . -
FIG. 6 is a diagrammatic environmental view of the inspection system ofFIG. 1 shown inspecting a structure free of sub-surface flaws as revealed by the inactivity of the indicator. -
FIG. 7 is a diagrammatic environmental view of the inspection system ofFIG. 1 shown inspecting a structure having sub-surface flaws as revealed by the activation of the indicator. -
FIG. 8 is a diagrammatic environmental view of the inspection system ofFIG. 1 shown inspecting the bondline integrity of a repair patch applied to the damaged structure ofFIG. 7 . -
FIG. 9 is a block diagram representing a method of inspecting a structure, the method in accordance with at least one other embodiment of the present disclosure. - The present disclosure now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the disclosure are shown. Indeed, the disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.
- An
inspection system 100 not according to the present invention is shown inFIG. 1 . The inspection system includes an analog signal-processing portion 102 and adigital processing portion 104. With regard to the analog signal-processing portion 102 of theinspection system 100, anoscillator 110 produces asinusoidal reference signal 111 that is applied to a combination of aresistor 112 and an ultrasonic transducer 114. The reference signal is generally preset to a frequency associated with the natural resonating frequency for a given ultrasonic transducer. When the ultrasonic transducer 114 is placed in contact and coupled through a liquid medium with a layered structure under inspection, the complex impedance of the transducer 114 is affected by the physical characteristics of the structure. Thus, theresponse signal 115 developed by the transducer 114 has phase and amplitude characteristics that are generally representative of the structure under inspection, and that are more particularly representative of the locations of defects such as bond flaws between the various layers of the structure. Theresponse signal 115 is applied to abuffer amplifier 116, which produces thesignal 117 that has phase and amplitude characteristics derived from those ofresponse signal 115. - The
sinusoidal signal 111 is further applied to an invertingamplifier 118, which, in conjunction with apotentiometer 120, produces asignal 121. Thereference signal 111 is also applied to anintegrating amplifier 122, which, in conjunction with an invertingamplifier 124 andpotentiometer 126, produces asignal 127.Signal 121 andsignal 127 represent quadrature-phase separated components of theresponse signal 115 developed by the transducer 114. - The signals 121,127, and 117 are applied to a
summing junction 132 to produce asignal 133, which represents the complex impedance of the transducer 114 as affected by any flaws present in the bonding between layers of a laminate structure under inspection. Thesignal 133 is applied to abuffer amplifier 134, theoutput signal 135 of which is applied to one terminal of apotentiometer 136. Asignal 137, which is an attenuated form of thesignal 133, then reaches anamplifier 138, the output of which is applied to a pair of synchronous demodulator andfilter circuits circuits signal 133, reference signals 143 and 145 are provided respectively byvoltage comparators - The 152 and 154 circuits respectively provide the first and second component signals 153 and 155. The
first component signal 153 may be mathematically described as Ep(cos(phi)), and thesecond component signal 155 as Ep(sin(phi)), where phi represents the phase characteristic of thesignal 133. Thus, the first and second component signals 153 and 155 have amplitudes that are proportional to quadrature-phase separated components of thesignal 133 which, when the transducer 114 is placed in contact or coupling with a structure under inspection, represents the condition of the structure. - Analog signal-processing in complex impedance plane analysis circuits is described in further detail in the
U.S. Patent No. 4,215,583, which issued to Botsco et al. on August 5, 2003 . In the Botsco patent, quadrature-phase separated components of a sinusoidal signal are used as coordinates in two-dimensional displays that represent vector tips in a complex impedance plane and that convey information relating to the amplitudes and phases of signals influenced by bond flaws within an inspected structure. It is therefore well understood in the prior art that the first and second component signals 153 and 155 can be related to impedance plane coordinates. Thus, the impedance plane coordinates described herein are determined by sampling the first and second component signals 153 and 155 respectively at the 152 and 154 circuits. - The
digital processing portion 104 of thesystem 100 receives the first and second component signals 153 and 155, and, as described in the following, anindicator 106 alerts an operator to the presence of a bond flaw when the transducer 114 is disposed into contact or coupling with a damaged or delaminated layered structure without regard to whether a typical operator views a two-dimensional display. This represents a significant advantage provided by embodiments of the present disclosure with regard to reducing the training and experience required of operators conducting inspections of laminated structures. Nonetheless, the first and second component signals 153 and 155, and other signals generated by or coursing through thesystem 100, may be available at test points within the circuit for sampling, analysis, and display by trained specialists. - The
digital processing portion 104 comprises an analog-to-digital converter (ADC) 160, which receives the first and second component signals 153 and 155 and generates respectively corresponding digital data signals 163 and 165. The digital data signals 163 and 165 are communicated to a programmable logic chip (PLC) 162. ThePLC 162 is programmed to analyze the corresponding digital data signals while calculating the impedance plane relationships between the signals and activating anindicator 106, which can be, for example, a light-emitting diode (LED) or other light source, when evidence of the presence of a disbond or other flaw is detected. The conditions under which thePLC 162 activates theindicator 106 are described in the following. - In
FIG. 2 , an example of areference signal 111 produced by the oscillator 110 (FIG. 1 ) is shown. Thefirst axis 202 represents time and thevertical axis 204 represents time-varying voltage values. WhileFIG. 2 relates generally to other time and voltage domains, in this example thereference signal 111 has a maximum amplitude of several volts and a frequency of approximately 239 kilo-Hertz. Thereference signal 111 is shown with several curves representing the response signals 115 developed by the transducer 114 under several different load conditions. It should be understood thatFIGS. 2-5 depict simulated signals and coordinates determined therefrom. - In
FIG. 2 , afirst response signal 115A corresponds to a calibration condition and is exhibited when the activated transducer 114 (FIG. 1 ) is disposed into contact or coupling with a good structure that is free of disbonds and flaws in the vicinity of the transducer. Asecond response signal 115B corresponds to a lift-off condition and is exhibited, upon activation by theoscillator 110, when the transducer 114 is out of coupling with a surface to be inspected. Athird response signal 115C corresponds to an inspection condition and is exhibited when the activated transducer 114 is disposed into contact or coupling with a structure under inspection. Thethird response signal 115C has phase and amplitude characteristics that differ from those of thefirst response signal 115A. Thus, thethird response signal 115C provides evidence that the structure under inspection may have a disbond or other defect in the vicinity of the transducer. - In
FIG. 3 , the signals depicted inFIG. 2 are represented as coordinates disposed within a two-dimensional complex impedance plane 300 defined by afirst axis 302 and asecond axis 304, which is perpendicular to thefirst axis 302. The impedance plane coordinates 315A, 315B, and 315C inFIG. 3 correspond respectively to the first, second, and third response signals 115A, 115B, and 115C inFIG. 2 . Each of the impedance plane coordinates 315A, 315B, and 315C inFIG. 3 are defined by a first axis coordinate and a second axis coordinate, values of which are determined as shown inFIG. 2 . Each second axis coordinate inFIG. 3 represents a measured voltage value for the respectively corresponding response signal at thetime 206 of the zero voltage crossing of thereference signal 111 inFIG. 2 . That is, for example, the second axis coordinate 304B of the impedance plane coordinates 315B inFIG. 3 represents the value of the response signal 115B inFIG. 2 at thetime 206. Each first axis coordinate inFIG. 3 represents a measured voltage value for the respectively corresponding response signal at thetime 208 inFIG. 2 . That is, for example, the first axis coordinate 302B of the impedance plane coordinates 315B inFIG. 3 represents the value of the response signal 115B inFIG. 2 at thetime 208. - The time 208 (
FIG. 2 ) is spaced from thetime 206 along thetime axis 202 by one quarter of the oscillatory period of thesinusoidal reference signal 111. Thus, in terms of the angular phase of thesinusoidal reference signal 111, thetime 208 can be described as disposed ninety degrees from the zero-voltage crossing, attime 206, of thereference signal 111. Furthermore, the first axis and second axis coordinates inFIG. 3 can be described as quadrature-phase separated components of the response signals to which the impedance plane coordinates respectively correspond. It should be understood that, while they are graphically illustrated together inFIG. 2 , the response signals 115A, 115B, and 115C, are not generated simultaneously as they represent varying physical dispositions of the transducer 114 (FIG. 1 ). It should be further understood that thetimes sinusoidal reference signal 111, such that thetimes - As the impedance plane coordinates 315A in
FIG. 3 correspond to thefirst response signal 115A (FIG. 2 ) of the calibration condition with the activated transducer disposed into contact or coupling with a good structure, thecoordinates 315A are identified herein as examples of impedance-plane calibration coordinates 315A. Similarly, thecoordinates 315B inFIG. 3 are identified herein as impedance plane lift-off coordinates 315B, and thecoordinates 315C are identified as impedance plane inspection coordinates 315C. - The
PLC 162 inFIG. 1 receives the digital data signals 163 and 165, and is prompted to record these signals when a user actuates first andsecond switches first switch 170, the user intends the condition of the transducer 114 to serve as the calibration condition. Thus, upon actuation of thefirst switch 170, thePLC 162 records the digital data signals 163 and 165 as impedance plane calibration coordinates along thefirst axis 302 andsecond axis 304, respectively, inFIG. 3 . By actuation of thesecond switch 172, the user intends the condition of the transducer to serve as the lift-off condition. Thus, upon actuation of thesecond switch 172, thePLC 162 records the digital data signals 163 and 165 as impedance plane lift-off coordinates along thefirst axis 302 andsecond axis 304, respectively. - Once the impedance plane calibration coordinates and lift-off coordinates are established, the PLC 162 (
FIG. 1 ) defines a lift-off translation function that may be applied to the incoming digital data signals 163 and 165 to translate from impedance plane inspection coordinates into a lift-off coordinate system. The disposition of the inspection coordinates may vary in time as the user moves the transducer 114 into various positions along a structure under inspection and may encounter varying structure conditions such as defects. Thus the impedance plane inspection coordinates 315C inFIG. 3 may vary in real-time. As thethird response signal 115C inFIG. 2 has phase and amplitude characteristics that differ from those of thefirst response signal 115A, the inspection coordinates 315C in this example do not coincide with the calibration coordinates 315A. Thus, the inspection coordinates 315C provide evidence that the structure under inspection may have a disbond or other defect in the vicinity of the transducer. - Generally, when the transducer 114 is disposed into contact or coupling with a structure in the vicinity of a defect such as a disbond between layers of the structure, the determined impedance-plane inspection coordinates will typically fall along a spiral path. For example, a
simulated spiral path 306 is shown inFIG. 3 . Thespiral path 306 spirals inward from the lift-off coordinates 315B, which correspond to zero depth, to the calibration coordinates 315A, which correspond to the depth of a good undamaged structure. Typical inspection coordinates corresponding to disbonded or damaged portions of an inspected structure will typically fall somewhere along thespiral path 306 such that the position of the inspection coordinates along the path reveals the depth of a detected disbonded or damaged layer of the structure. Relatively shallow disbonds will typically be represented by inspection coordinates along thespiral path 306 toward the lift-off coordinates 315B. Relatively deep disbonds will typically be represented by inspection coordinates toward the calibration coordinates 315A. InFIG. 3 , the inspection coordinates 315C fall along an outer portion of thespiral path 306, and toward the lift-off coordinates 315B. This provides evidence that the structure under inspection may have a shallow disbond or other defect in the vicinity of the transducer. - The PLC 162 (
FIG. 1 ) generally rotates the impedance plane coordinates represented inFIG. 3 using the lift-off translation function. Such rotations produce rotated impedance plane coordinates as shown inFIG. 4 and5 , which represent examples of embodiments of the present disclosure with regard to conditions under which thePLC 162 activates the indicator 106 (FIG. 1 ). In the example ofFIG. 4 , thePLC 162 automatically rotates the impedance plane coordinates 315A, 315B, and 315C until the resulting rotated calibration coordinates 415A and lift-off coordinates 415B reach thefirst axis 302. As shown inFIG. 4 , such a rotation produces rotated inspection coordinates 415C and the rotatedspiral path 406. Points along the rotatedspiral path 406 inFIG. 4 relate in one-to-one correspondence with points along thespiral path 306 inFIG. 3 . - The lift-off translation function effectively rotates the impedance plane coordinates, which rotating may be described as equivalent to shifting the times at which the voltage values of response signals are measured in determining the coordinates. That is, each of the rotated impedance plane coordinates in
FIG. 4 has a second axis coordinate representing a voltage value measured at thetime 210 inFIG. 2 , and a first axis coordinate representing a measurement at thetime 212. The respective correspondence of the calibration coordinates 415A (FIG. 4 ), lift-off coordinates 415B, and inspection coordinates 415C with the response signals 115A (FIG. 2 ), 115B, and 115C is maintained throughout the rotation. The shiftedtimes times FIG. 4 . Thus, like thetimes times FIG. 2 are separated by one quarter of the oscillatory period of thesinusoidal reference signal 111. Therefore, the rotated first axis and second axis coordinates inFIG. 4 can be described as quadrature-phase separated components of the response signals to which the rotated impedance plane coordinates respectively correspond. - In the example of
FIG. 4 , the PLC 162 (FIG. 1 ) activates theindicator 106 if the rotated inspection coordinates 415C are at least disposed above thefirst axis 302. This generally indicates an alarm condition wherein the rotated inspection coordinates, such as inspection coordinates 415C, are not coincident with the rotated calibration coordinates 415A. Furthermore, in the example ofFIG. 4 , the PLC 162 (FIG. 1 ) may be configured to activate theindicator 106 if the rotated inspection coordinates 415C are at least disposed above thefirst axis 302, and spaced from the first axis by at least apreset threshold 408. As shown inFIG. 1 , theinspection system 100 comprises anadjustment device 174, such as a turn-potentiometer, for adjustment of thepreset threshold 408, which may be adjusted to avoid spurious alarm indications when, for example, rotated inspection coordinates fall negligibly above the rotated calibration coordinates 415A. - In the example of
FIG. 5 , the PLC 162 (FIG. 1 ) automatically rotates the impedance plane coordinates 315A, 315B, and 315C (FIG. 3 ) until the resulting rotated lift-off coordinates 515B (FIG. 5 ) are disposed above thefirst axis 302 and spaced from the first axis by at least thepreset threshold 408. As shown inFIG. 5 , such a rotation produces rotated calibration coordinates 515A, rotated inspection coordinates 515C, and the rotatedspiral path 506. In the example ofFIG. 5 , the PLC 162 (FIG. 1 ) activates theindicator 106 if the rotated inspection coordinates 515C are at least disposed above thefirst axis 302 and spaced from the first axis by at least thepreset threshold 408. In this example, the indicator 106 (FIG. 1 ) is activated to alert an operator if liquid coupling between the transducer 114 and an inspected structure is lost. Such a loss of coupling may cause the generation of rotated impedance plane coordinates near or at coincidence with the rotated lift-off coordinates 515B. Thus, in the example ofFIG. 5 , an operator is alerted when inadvertent lift-off and coupling-loss conditions occur, prompting the operator to restore couplant or re-scan the area. - Thus, with further regard to
FIG. 5 , the disposition of rotated inspection coordinates above thepreset threshold 408 causes activation of the indicator 106 (FIG. 1 ). This establishes one or more depth ranges within which theinspection system 100 indicates disbonds within an inspected structure. For example, a first depth range is established along afirst portion 510 of the rotatedspiral path 506 between the rotated lift-off coordinates 515B and afirst point 512 defined where the rotatedspiral path 506 reaches thepreset threshold 408. A second depth range is established above thethreshold 408 and along asecond portion 514 of the rotatedspiral path 506 between second andthird points spiral path 506 reaches thepreset threshold 408. Thefirst portion 510 represents an outer portion of the rotatedspiral path 506, and thesecond portion 514 represents an inner portion of the rotatedspiral path 506. Thus, thefirst portion 510 represents a shallow depth range for detected disbonds and thesecond portion 514 represents a deeper depth range. Nonetheless, in this example, rotated inspection coordinates falling along either thefirst portion 510 or thesecond portion 514 of the rotatedspiral path 506 cause activation of the indicator 106 (FIG. 1 ) to alert an operator to the likely presence of a disbond in an inspected structure. Activation of the indicator in thefirst portion 510 is a condition universal to all structures, independent of the operator choice of structure for initial calibration coordinates 315A. - An embodiment of the inspection system 100 (
FIG. 1 ) is shown in various simulated inspection scenarios inFIGS. 6-8 . In this embodiment, many components of theinspection system 100 are disposed within and protected by aportable housing 600. Aprobe device 602 that includes the ultrasonic transducer 114 (FIG. 1 ) is connected to the remainder of thesystem 100 by acable 604 so that the probe device can be moved about and coupled to structures while thehousing 600 is held within view of an operator. The first andsecond switches inspection device 100 shown inFIGS. 6-8 , theadjustment device 174, which establishes the preset threshold 408 (FIG. 4 ), is intended for use by qualified NDI specialists and is therefore hidden within thehousing 600. Theindicator 106 is visible along the exterior of the housing so that an operator is made readily aware when an alert condition occurs. Apower switch 606, when actuated, activates theinspection system 100 for use. - Prior to determining whether damages are present in a structure, the inspection device is calibrated by disposing the probe device 602 (
FIG. 6 ) against a good structure that is free of disbonds and flaws in the vicinity of the probe device, and thefirst switch 170 is actuated. This establishes calibration coordinates, such as the calibration coordinates 315A inFIG. 3 . The operator may choose a portion of a structure under inspection, under the assumption that the portion is free of flaws. However, the assurance of the calibration of theinspection system 100 following such a calibration procedure may be as questionable as any assumption that a good portion of a structure was interrogated. Thus, a calibration structure can be provided in order to assure that calibration is completed on a well characterized material sample. The operator furthermore lifts theprobe device 602 from contact with any structure and actuates thesecond switch 172 to establish lift-off coordinates, such as the lift-off coordinates 315B inFIG. 3 . The embodiment of theinspection system 100 shown inFIGS. 6-8 is configured as described herein with regard toFIG. 5 . Thus, once the impedance plane calibration coordinates and-lift-off coordinates are established, the inspection system is ready for use in inspecting structures. Theindicator 106 will be activated to alert an operator if rotated inspection coordinates, for example coordinates 515C (FIG. 5 ), are disposed above thefirst axis 302 and spaced from the first axis by at least thepreset threshold 408. -
FIG. 6 depicts anexemplary laminate structure 640 capable of being used on any number of structures, such as those found on airplanes, automobiles and other vehicles, or any other structure that can benefit from a light, yet strong material. Thelaminate structure 640 has a front-surface 642 and a back-surface 644, and is composed of multipleindividual laminate sheets 646. The laminate sheets are joined together by a bonding material. Theexemplary laminate sheets 646 are composed of sheets of graphite fibers joined by a bonding material composed of an ester based resin. However, it should be appreciated that these descriptions relate to sheets constructed of other materials. Such other materials include, but are not limited to: carbon-based fabrics; metal foils; bonded metal skins; and polymer-based fabrics such as Kevlar®. Furthermore, while thelaminate structure 640 ofFIG. 6 is formed using an ester-based resin, these descriptions relate as well to other bonding materials. - In the course of normal use, laminate materials are subject to accidental damages. For example, where laminate materials are used to cover the front surfaces of aircraft wings, impact damages from birds and airborne debris can occur with every flight. In some instances the resultant damage will be very light, while in other instances the damage may be moderate to severe. For example, the
laminate structure 640 inFIG. 6 is depicted as being so lightly damaged that a marking visibly apparent at animpact site 650 is merely superficial and represents no threat to the integrity of the structure. Thus, in the inspection scenario ofFIG. 6 , theindicator 106 is not activated to alert the operator that any damages are detected below theprobe device 602. The rotated inspection coordinates in this scenario are coincident with the rotated calibration coordinates 515A (FIG. 5 ), are disposed below thethreshold 408, and are indicative of a structure free of damages. - In
FIG. 7 , theinspection system 100 inspects alaminate structure 740 wherein flaws such as delaminations reside. In this figure, theimpact site 750 is disposed above a damaged region of the structure. The damage likely began at the impact site along thefront surface 742 of the structure and propagated toward theback surface 744 in an expanding cone pattern ofdisbonds 752 as illustrated. Such cone patterns are typical in damaged laminate structures as damages can extend both deeply into a structure and laterally around an impact site. Thus, when an impact site is observed on a surface, it is good practice to inspect a structure for hidden damages residing below surface portions that surround the impact site. Thus, inFIGS. 6 and 7 , theprobe device 602 is pressed against structures near theimpact sites FIG. 6 , with an understanding that hidden damages typically exhibit cone patterns, the operator can determine that hidden damages are not likely present. In the scenario ofFIG. 7 , the rotated inspection coordinates 515C (FIG. 5 ) are disposed above thefirst axis 302 and spaced from the first axis by at least thepreset threshold 408. Thus, theindicator 106 is activated to alert the operator that sub-surface damages are detected. - In
FIG. 8 , theinspection system 100 inspects the bondline integrity of acomposite repair patch 800 applied to the damagedstructure 740 ofFIG. 7 . Bondline integrity relates to the quality of the bond between a patch and the surface of a structure. If the bond has porosity or voids, the patch may become detached when the structure is returned to service. For example, a repair patch applied to the wing tip or other exterior component of a jet aircraft can be exposed to extreme conditions and can become detached and lost if the bondline integrity of the patch is not sound. Typical composite repair patches in the airline industry are either four or eight plies thick. InFIG. 8 , theinspection system 100 has been initialized for inspecting the bondline integrity of a four-ply patch 800. That is, impedance plane calibration coordinates, collected using a calibration shim exceeding the thickness of the four-ply patch, and lift-off coordinates have been established. Theindicator 106 is not activated inFIG. 8 . This condition provides assurance to the operator that therepair patch 800 is properly applied to the damaged structure at least in the vicinity of the current position of theprobe device 602. In performing a thorough inspection, the operator may move the probe device along the perimeter of the patch to determine whether the patch is well attached to thestructure 740. -
FIG. 9 is a flow chart representing a method, according to at least one embodiment of the disclosure, of inspecting a structure. The inspected structure may be, for example, an aircraft component constructed of multiple layers of composite material. Themethod 900 represented inFIG. 9 initiates atstep 910, at which step an ultrasonic transducer is coupled with a first structure portion. The first structure portion is assumed or confirmed to be free of defects, and may be, for example, a calibration sample of material intended for use in calibrating the inspection system 100 (FIG. 7 ). - In step 920 (
FIG. 9 ), a sinusoidal first signal is generated by the ultrasonic transducer and impedance plane calibration coordinates are determined, the calibration coordinates corresponding to quadrature-phase separated components of the first signal. For example, instep 920, thefirst response signal 115A inFIG. 2 may be generated as the sinusoidal first signal, and the impedance-plane calibration coordinates 315A inFIG. 3 may be determined. - In step 930 (
FIG. 9 ), the ultrasonic transducer is lifted from the first structure portion. Instep 940, a sinusoidal second signal is generated by the ultrasonic transducer and impedance plane lift-off coordinates are determined, the lift-off coordinates corresponding to quadrature-phase separated components of the second signal. For example, instep 940, the second response signal 115B inFIG. 2 may be generated as the sinusoidal second signal, and the impedance-plane lift-off coordinates 315B inFIG. 3 may be determined. - Once the impedance plane calibration coordinates and lift-off coordinates are established, the inspection of a structure, such as an aircraft component constructed of multiple layers of composite material, commences in step 950 (
FIG. 9 ). Instep 950, the ultrasonic transducer is coupled with a structure portion to be inspected. For example, an aircraft may be subject to a pre-flight visual inspection and the impact site 750 (FIG. 7 ), which represents a surface marking, dent, or scratch may come to the attention of a pre-flight inspector. The inspector may not be able to visibly determine whether serious damage is present, and a decision should be made as to whether the aircraft is fit for flying service. Accordingly, in this example, the inspector couples theprobe device 602, which includes the ultrasonic transducer 114 (FIG. 1 ), with thestructure 740 under inspection near the impact site as shown inFIG. 7 . - In step 960 (
FIG. 9 ), a sinusoidal third signal is generated by the ultrasonic transducer and impedance plane inspection coordinates are determined, the inspection coordinates corresponding to quadrature-phase separated components of the third signal. For example, instep 960, thethird response signal 115C inFIG. 2 may be generated as the sinusoidal third signal, and the impedance-plane inspection coordinates 315C inFIG. 3 may be determined. - Rotations of the calibration coordinates, lift-off coordinates, and inspection coordinates are represented in
FIG. 9 to occur instep 970. It should be understood this represents that the coordinates are rotated without regard to whether this is accomplished simultaneously. For example, the calibration and lift-off coordinates may be rotated prior to the determination of the inspection coordinates instep 960. In any event, the calibration coordinates, lift-off coordinates, and inspection coordinates are rotated in themethod 900 at least until the calibration coordinates and lift-off coordinates reach a first axis. One example of such a rotation is represented inFIG. 4 , wherein the calibration, lift-off, and inspection coordinates are rotated until the calibration coordinates 415A and lift-off coordinates 415B reach thefirst axis 302. Another example of such a rotation is represented inFIG. 5 , wherein the calibration, lift-off, and inspection coordinates are rotated until the lift-off coordinates 415B are disposed above thefirst axis 302 and spaced from the first axis by at least thepreset threshold 408. - In
step 980, an indicator is activated if the rotated inspection coordinates are at least disposed above the first axis. Activation of the indicator represents a situation wherein an operator is alerted to the likely presence of a defect in the structure under inspection, for example, as shown inFIG. 7 . If the indicator is activated, the operator may perform further inspections and, if the structure under inspection is an aircraft component, the flight of the aircraft may be delayed or even cancelled. For example, the operator may summon NDI specialists who may utilize additional inspection devices and methods to determine the extent of the damages. - A
branch 990 is shown inFIG. 9 to illustrate optional additional iterations ofsteps 950 through 980. That is, in at least one embodiment of themethod 900, the ultrasonic transducer is disposed sequentially in multiple locations near the impact site. For example, the transducer might be moved among multiple locations that together surround the impact site. At any such location, the operator observes the indicator and determines whether further inspections are performed according to the judgment or training of the operator. The additional optional iterations represented bybranch 990 may be particularly advantageous in inspecting an aircraft component constructed of multiple layers of composite materials. Damages initiating at the surfaces of such constructions typically propagate in expanding cone-patterns into the structures. Thus, damages may be detected by conducting inspections at multiple surface portions surrounding an impact site. - A particular advantage of the inspection system 100 (
FIG. 6 ) resides in the simplicity of itsindicator 106. This, in a sense, provides go and no-go test results. An operator without sophisticated training in NDI techniques need not be confounded by complex impedance plane graphical displays. Such an operator can be informed, however, of whether or not significant damages likely reside in an inspected structure. If theindicator 106 is not activated during an inspection session, an inspected structure can be dispatched for use. On the other hand, if theindicator 106 is activated as shown inFIG. 7 , the operator can summon specialists trained in inspections, repairs, and repair assessments. - Though several advantages of embodiments of the present disclosure are described herein, it should be understood that other advantages and other embodiments of the present disclosure are within the scope of these descriptions. Indeed, many modifications and other embodiments of the disclosure set forth herein may come to mind to one skilled in the art to which the disclosure pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the disclosure is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
Claims (2)
- A method of inspecting a structure, the method comprising:coupling (90) an ultrasonic transducer (114) with a first structure portion free of defects, generating a sinusoidal first signal by the ultrasonic transducer, and determining impedance-plane calibration coordinates (315A,415A,515A) of a two-dimensional complex impedance plane (300) defined by a first axis (302) and a second axis (304) that is perpendicular to the first axis, and wherein the impedance plane calibration coordinates correspond to quadrature-phase separated components of the sinusoidal first signal and wherein each of the impedance-plane calibration coordinates are defined by a first axis coordinate and a second axis coordinate where the second axis coordinate represents a measured voltage value for the sinusoidal first signal at the time of zero crossing of the first axis of a reference sinusoidal signal (111) and the first axis coordinate represents a measured voltage value for the sinusoidal first signal at a time one quarter of the oscillatory period of the reference sinusoidal signal from the zero crossing;lifting (930) the ultrasonic transducer from the first structure portion, generating a sinusoidal second signal by the ultrasonic transducer, and determining impedance-plane lift-off coordinates (315B,415B,515B) of a two-dimensional complex impedance plane (300) defined by a first axis (302) and a second axis (304) that is perpendicular to the first axis, and wherein the impedance plane lift-off coordinates correspond to quadrature-phase separated components of the sinusoidal second signal and wherein each of the impedance-plane lift-off coordinates are defined by a first axis coordinate and a second axis coordinate where the second axis coordinate represents a measured voltage value for the sinusoidal second signal at the time of zero crossing of the first axis of the reference sinusoidal signal (111) and the first axis coordinate represents a measured voltage value for the sinusoidal second signal at a time one quarter of the oscillatory period of the reference sinusoidal signal from the zero crossing;coupling (950) the ultrasonic transducer with a structure portion to be inspected, generating a sinusoidal third signal by the ultrasonic transducer, and determining impedance-plane inspection coordinates (315C,415C,515C) of a two-dimensional complex impedance plane (300) defined by a first axis (302) and a second axis (304) that is perpendicular to the first axis, and wherein the impedance plane inspection coordinates correspond to quadrature-phase separated components of the sinusoidal third signal and wherein each of the impedance-plane calibration coordinates are defined by a first axis coordinate and a second axis coordinate where the second axis coordinate represents a measured voltage value for the sinusoidal third signal at the time of zero crossing of the first axis of the reference sinusoidal signal (111) and the first axis coordinate represents a measured voltage value for the sinusoidal signal at a time one quarter of the oscillatory period of the reference sinusoidal signal from the zero crossing;automatically rotating (970) the calibration coordinates, lift-off coordinates, and inspection coordinates until the calibration coordinates and lift-off coordinates reach the first axis (302); andactivating (980) an indicator (106) if the rotated inspection coordinates are at least disposed above the first axis and spaced from the first axis by at least a preset threshold (408).
- The method of claim 1, further comprising automatically rotating the calibration coordinates, lift-off coordinates, and inspection coordinates until the lift-off coordinates are disposed above the first axis and spaced from the first axis by at least the preset threshold, and activating the indicator if the rotated inspection coordinates are at least disposed above the first axis and spaced from the first axis by at least the preset threshold to indicate that the ultrasonic transducer is lifted from or has otherwise lost coupling with the structure portion to be inspected.
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US11/617,304 US7574915B2 (en) | 2006-12-28 | 2006-12-28 | Simplified impedance plane bondtesting inspection |
PCT/US2007/023456 WO2008088436A1 (en) | 2006-12-28 | 2007-11-06 | Simplified impedance plane bondtesting inspection by ultrasonic means |
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EP2097741A1 EP2097741A1 (en) | 2009-09-09 |
EP2097741B1 true EP2097741B1 (en) | 2014-04-09 |
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US8825498B2 (en) * | 2007-02-12 | 2014-09-02 | The Boeing Company | Ramp recorder and quick reporting tree data transmission method |
US9123189B2 (en) * | 2007-02-12 | 2015-09-01 | The Boeing Company | System and method for point-of-use instruction |
US8349104B2 (en) * | 2008-07-21 | 2013-01-08 | United Technologies Corporation | Method and assembly for validating bond line |
US8522615B1 (en) | 2010-11-30 | 2013-09-03 | The Boeing Company | Simplified direct-reading porosity measurement apparatus and method |
US9188672B2 (en) * | 2012-04-13 | 2015-11-17 | Defelsko Corporation | Ultrasonic measuring gauge |
US10222353B2 (en) * | 2015-03-18 | 2019-03-05 | The Boeing Company | Method and assembly for inspecting a partially cured repair patch prior to installation |
US10816513B2 (en) * | 2016-08-10 | 2020-10-27 | University Of South Carolina | Wireless damage assessment during manufacturing |
CN106770667B (en) * | 2016-12-22 | 2019-10-18 | 中航复合材料有限责任公司 | A kind of ultrasonic visualization imaging method detecting composite structure rib area |
US11131759B2 (en) * | 2017-05-09 | 2021-09-28 | Thornton Tomasetti, Inc. | System, device and method for in-water inspection of maritime vessel acoustic treatments |
US11624690B2 (en) * | 2019-03-12 | 2023-04-11 | The Boeing Company | Device and method for use in examining a composite structure |
US11686707B2 (en) | 2020-03-30 | 2023-06-27 | Verifi Technologies, Llc | System and method for real-time visualization of defects in a material |
US11860131B2 (en) | 2020-03-30 | 2024-01-02 | Verifi Technologies, Llc | System and method for portable ultrasonic testing |
US11754529B2 (en) | 2020-03-30 | 2023-09-12 | Verifi Technologies, Llc | System and method for evaluating defects in a material |
US11726065B2 (en) | 2020-03-30 | 2023-08-15 | Verifi Technologies, Llc | System and method for real-time visualization of defects in a material |
US11650183B2 (en) | 2020-03-30 | 2023-05-16 | Verifi Technologies, Llc | System and method for real-time degree of cure evaluation in a material |
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US3016735A (en) * | 1958-06-17 | 1962-01-16 | James S Arnold | Structural bond evaluation |
US3453872A (en) * | 1966-03-24 | 1969-07-08 | North American Rockwell | Eddy sonic inspection method |
US3564903A (en) * | 1968-05-20 | 1971-02-23 | Boeing Co | Bond failure detection in laminated structures using vibration response |
US4215583A (en) * | 1978-11-14 | 1980-08-05 | Ndt Instruments, Inc. | Apparatus and method for bondtesting by ultrasonic complex impedance plane analysis |
US4815001A (en) * | 1986-05-30 | 1989-03-21 | Crestek, Inc. | Ultrasonic wire bonding quality monitor and method |
US4862384A (en) * | 1987-08-03 | 1989-08-29 | Rockwell International Corporation | Method of measuring the dynamic viscosity of a viscous fluid utilizing acoustic transducer |
US4840066A (en) * | 1988-06-27 | 1989-06-20 | Ndt Instruments, Inc. | Ultrasonic thickness gauge having automatic transducer recognition and parameter optimization and method thereof |
JP2000005180A (en) * | 1998-06-25 | 2000-01-11 | Olympus Optical Co Ltd | Acoustic impedance measuring device |
US7222514B2 (en) * | 2004-06-21 | 2007-05-29 | The Boeing Company | Laminate material testing methods and systems |
GB2425179A (en) | 2005-04-14 | 2006-10-18 | Warwickshire Mfg Group | Assessing the quality of rivets by evaluating the complex valued electrical impedance of a piezoelectric ultrasonic transducer |
US7557570B2 (en) * | 2005-11-03 | 2009-07-07 | The Clock Spring Company L.P. | System and method for producing color contour maps of surface defects of high pressure pipelines |
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2006
- 2006-12-28 US US11/617,304 patent/US7574915B2/en active Active
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- 2007-11-06 EP EP07867383.7A patent/EP2097741B1/en active Active
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US4096755A (en) * | 1977-08-31 | 1978-06-27 | The Boeing Company | Ultrasonic inspection apparatus |
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EP2097741A1 (en) | 2009-09-09 |
US20080156096A1 (en) | 2008-07-03 |
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WO2008088436A1 (en) | 2008-07-24 |
US7574915B2 (en) | 2009-08-18 |
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